Currently, magnetic disk devices, solid-state storage drives (SSDs) and the like are used as storage devices. An SSD comprises, for example, stacked circuit boards and an enclosure accommodating these circuit boards. Memory devices such as NAND flash memories are mounted on each circuit board. A heat-producing component such as a semiconductor device is mounted on at least one of the circuit boards. Adjacent circuit boards are connected to each other via a connector. When three or more circuit boards are stacked, the space between the circuit boards becomes narrow and the heat of the heat-producing component cannot be easily dissipated. As a result, components mounted on the circuit boards are heated and the temperature rises in some cases.